Structural Integrity Assessment of Nuclear Spent Fuel Canisters Using Guided Waves

Abstract

Dry storage canisters (DSC) are primarily used for storing nuclear spent fuel rods for an extended period. Due to the critical role of these assemblies, periodic inspections are necessary for mitigating potential accidents and subsequent release of radioactive material to the environment. Aside from visual inspections, the most effective approach to evaluate their structural integrity is by non-destructive techniques. In this work, we utilize helical guided ultrasonic waves (HGUW) to develop a non-destructive scheme for the structural health monitoring of DSC. These waves share identical characteristics with traditional Lamb waves but travel circumferentially in cylindrical waveguides. The proposed methodology is comprised of instrumenting the canister with a permanently attached network of piezoelectric patches (PZT) capable of transmitting and receiving high frequency HGUW. Using the data collected from the HGUW inspection, a probabilistic imaging technique is employed to localize defects within the span of the PZT arrays. Furthermore, an investigation of the scattering of the fundamental Lamb modes from different cracks and notches is investigated and the patterns are exploited for improving the fidelity and accuracy of the imaging method. Experiments have been conducted on various specimens including a 6-in-diameter cylinder in the lab and an actual DSC with a diameter of approximately 6 feet.